We study intracellularly the physiology of single retinal neurons in cats and pigeons. Individual neurons stained through the microelectrode with horse-radish peroxidase (HRP), are classified anatomically after physiological recordings. Using the resolution of the electron microscope, we can then identify synaptic contacts made between the stained cells, which have electron opaque profiles, and other retinal neurons such as photoreceptor, horizontal, bipolar, amacrine and ganglion cells. The response properties of flat and invaginating cone bipolar cells of the cat and the horizontal cells of the pigeon have been identified. The morphology of individual neurons in monkey, cat and pigeon retinas is also studied at the light and electron microscopic levels using Golgi impregnation. The connections between primate bipolar cells and cones have been so observed. A new type of invaginating bipolar, the 'diffuse' variety, has been identified. Primate retinas fixed for ultrastructure demonstrate contacts between photoreceptor terminals and their variation in density and type with retinal location. Structural differences in cone conducting fibers and pedicles occur between foveolar and extrafoveolar cones.